Remove unused dependencies and upgrade remaining dependencies.

package.json

@@ -19,24 +19,19 @@
     "client library"
   ],
   "dependencies": {
-    "async": "^2.0.0",
-    "gtoken": "^1.1.0",
-    "lodash.noop": "^3.0.0",
-    "jws": "^3.1.0",
-    "request": "^2.74.0",
-    "string-template": "^1.0.0"
+    "gtoken": "^1.2.1",
+    "lodash.noop": "^3.0.1",
+    "jws": "^3.1.4",
+    "request": "^2.79.0"
   },
   "devDependencies": {
-    "coveralls": "^2.11.1",
-    "istanbul": "^0.3.2",
+    "coveralls": "^2.11.15",
+    "istanbul": "^0.4.5",
     "keypair": "^1.0.0",
-    "jshint": "^2.5.5",
+    "jshint": "^2.9.4",
     "jsdoc": "^3.4.3",
-    "mkdirp": "^0.5.0",
-    "mocha": "^3.1.2",
-    "nock": "^9.0.2",
-    "rimraf": "^2.2.8",
-    "minimist": "^1.1.0"
+    "mocha": "^3.2.0",
+    "nock": "^9.0.2"
   },
   "scripts": {
     "lint": "jshint lib test",